U.S. patent number 4,788,329 [Application Number 06/926,068] was granted by the patent office on 1988-11-29 for preparation of cyclohexyl mono- and diurethanes and isocyanates derived therefrom by addition of methylcarbamate to limonene, process and compositions.
This patent grant is currently assigned to American Cyanamid Company. Invention is credited to Laurence J. Nummy.
United States Patent |
4,788,329 |
Nummy |
November 29, 1988 |
Preparation of cyclohexyl mono- and diurethanes and isocyanates
derived therefrom by addition of methylcarbamate to limonene,
process and compositions
Abstract
A process is disclosed whereby mono- and diurethane cyclohexyl
derivatives are obtained corresponding to the Lewis acid-catalyzed
addition reaction of dipentene and methyl carbamate at a
temperature of from about 40.degree. to about 150.degree.C. The
mono- and diurethane cyclohexyl derivatives are pyrolytically
converted to other corresponding mono- and diisocyanate cyclohexyl
derivatives. Novel vinyl unsaturated monoisocyanate cyclohexyl
derivatives useful as reactants for polyfunctional compounds to
produce cured compositions are disclosed.
Inventors: |
Nummy; Laurence J. (Newburgh,
NY) |
Assignee: |
American Cyanamid Company
(Stamford, CT)
|
Family
ID: |
25452695 |
Appl.
No.: |
06/926,068 |
Filed: |
November 3, 1986 |
Current U.S.
Class: |
560/330; 560/115;
560/345 |
Current CPC
Class: |
C07C
265/10 (20130101); C08G 18/728 (20130101); C07C
265/00 (20130101) |
Current International
Class: |
C08G
18/00 (20060101); C08G 18/72 (20060101); C07C
119/045 () |
Field of
Search: |
;560/330 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Lesiak, Pol, J. Chem., 52, pp. 927-932, (1978)..
|
Primary Examiner: Shippen; Michael L.
Attorney, Agent or Firm: Kelly; Michael J. Flynn; Steven
H.
Claims
We claim:
1. A compound having the formula ##STR9##
2. A compound as defined in claim 1 further comprising a compound
having the formula ##STR10##
Description
FIELD OF THE INVENTION
The present invention relates to a novel process for the
preparation of cyclohexyl mono- and diurethanes and their
correspondingly derived mono- and diisocyanates, and to novel
monoisocyanates produced thereby, and to curable compositions which
comprise such monoisocyanates. More particularly, the invention
relates to the preparation of the aforementioned compounds by the
addition of methyl carbamate to limonene or dipentene in the
presence of an acid to form cyclohexyl carbamate derivatives
including mono- and diurethane compounds which can be cracked in
hot inert solvent to give the corresponding cyclohexyl isocyanates.
These cyclohexyl isocyanates comprise diisocyanates and novel
monoisocyanate compounds, both of which are useful as reactants in
curable resin compositions and in other plastic applications.
BACKGROUND OF THE INVENTION
Various methods have been employed to produce isocyanate compounds.
It is known that diamine or monoamine derivatives can be reacted
with phosgene at a temperature of about 100.degree. C. for about 28
hours. The by-product hydrogen chloride and excess phosgene are
removed by blowing nitrogen through the liquid reaction mixture and
recovering the desired mono- and diisocyanates.
In another approach, Klein and Gerhard, Forsch Technol. 1983 CA
100:68763q, report that the unsaturated compound limonene can be
treated with hydrogen cyanide and subsequently with phosgene to
form a diisocyanate derivative, which is thermally rearranged to
diamine dipentene, which in turn, can be treated with phosgene to
prepare a diisocyanate of the formula ##STR1## Drawbacks of this
process are the toxicity of the hydrogen cyanide and phosgene, and
corrosion problems associated with the by-product hydrochloric
acid.
The difficulties with direct phosgenations have led to the
development of non-phosgenation routes, and these generally involve
the pyrolytic thermolysis or cracking of carbamic acid esters or
urethanes.
It is also known that isocyanate compounds can be prepared by the
reaction of corresponding olefins with isocyanic acid, by reaction
of the corresponding halide with an alkali metal isocyanate, and by
reaction of the corresponding halide with isocyanaic acid.
Merely by way of illustration, it has been shown in Bortnick, U.S.
Pat. No. 2,692,275, that 1,8-diisocyanato-p-menthane can be
prepared by pyrolyzing the corresponding carbamate in the presence
of a basic catalyst such as the water-soluble metal hydroxides or
alkoxides or the water-insoluble metallic oxides or hydroxides.
Mueller and Merten, Chem. Ber. 98, 1097-1110 (1965), carry out the
alkylation of urethane, i.e., carbamic acid ethyl ester with a
number of cyclic and noncyclic olefins in the presence of acid
catalyst to form N-substituted urethanes. The N-substituted
urethanes are converted to corresponding isocyanates by
"transurethanation", that is, by reacting industrially available
higher-boiling mono- or polyisocyanates, e.g., tolylene
diisocyanates with the N-substituted urethanes at 200.degree.14
240.degree. C. to release isocyanates.
These various processes are disadvantageous for one or more
reasons, such as that the materials are difficult to handle or are
corrosive, the yields are poor, expensive reactants are required
and the products are difficult to recover.
In Singh, Chang and Forgione, U.S. Pat. No. 4,439,616, tertiary
aralkyl isocyanates are produced by thermal cracking of
corresponding urethanes formed by the addition of corresponding
olefins, e.g., diisopropenyl benzene and carbamic acid esters,
e.g., methyl carbamate, at moderate temperatures and in the
presence of an acid catalyst. There is no hint or suggestion in
Singh et al. that wholly non-aromatic mono- and diisocyanate
compounds can be produced by the addition of an olefinic
substituted cycloalkene and a carbamic acid ester.
It has now been discovered that wholly non-aromatic cyclohexyl
isocyanate compounds can be prepared by a new route of synthesis
involving catalyzed pyrolysis of urethanes that have themselves
been synthesized by the addition of alkyl carbamate, such as methyl
carbamate, to the compound limonene or dipentene [1
methyl-4-(1-methylethenyl)cyclohexene].
It is an important object of this invention to produce cyclohexyl
isocyanates utilizing non-corrosive, low-cost starting materials
such as limonene or dipentene and methyl carbamate in a simple
process yielding the desired isocyanates whereby they are readily
recovered and purified.
SUMMARY OF THE INVENTION
In accordance with this invention mono- and diisocyanate cyclohexyl
compounds are prepared by the addition of methylcarbamate to
limonene to form mono- and diurethanes followed, if desired, by the
thermal cracking of such urethanes to form the isocyanate and the
free alcohol.
The present invention thus provides a process for production of
urethanes of the formulae: ##STR2## or a mixture of any of (I),
(II) and (III) wherein R is alkyl of from about 1 to about 30,
preferably 1 to 18, carbon atoms, by reacting
(a) an unsaturated cyclic hydrocarbon of the formula ##STR3##
with
(b) at least 2 moles per mole of (a) of (b) of carbamic acid ester
of the formula
wherein R is as defined above, in the presence of
(c) an effective catalytic amount of acid at a temperature of from
about 40.degree. to about 150.degree. C. until formation of said
urethane compounds (I), (II) or (III), or a mixture of any of them
is substantially complete.
Also contemplated by this invention is a process for the production
of mono- and diisocyanate cyclohexyl compounds which comprises
heating the urethane product (I), (II) and (III) or a mixture of
any of the foregoing at a temperature in the range of from about
200.degree. C. to about 300.degree. C. until formation of an
isocyanate compound of the formulae: ##STR4## or a mixture of any
of compounds (IV), (V) and (VI) is substantially complete.
Also provided according to the present invention are compounds
selected from those of the formulae: ##STR5## or a mixture of said
compounds. These compounds can be vinyl addition polymerized or
copolymerized to produce urethanes which can form curable
compositions with polyhydric compounds, e.g., polyols, polyamines,
and with water.
DETAILED DESCRIPTION OF THE INVENTION
The limonene or dipentene, 1-methyl-4-(1-methylethenyl)cyclohexene,
useful as a starting material in accordance with this invention and
represented by the formula ##STR6## can be isolated from the
ethereal oils of various natural plants including lemon, orange,
caraway, dill, bergamot, and mandarin peel oil, the latter as
reported by Kugler and Kovats, Helv Chim Acta 46, 1480 (1963).
The carbamic esters used as component (b) herein are compounds
represented by the general formula: ##STR7## wherein R is as
defined above, i.e., alkyl of from about 1 to about 30 carbon
atoms, straight chain or branched. Examples of suitable alkyl
carbamates are methylcarbamate, ethylcarbamate, propylcarbamate,
butylcarbamate, octadecyl carbamate, 2-ethylhexylcarbamate,
triacontyl carbamate, and the like. Especially preferred for use
herein is the compound methylcarbamate also known as carbamic acid
methyl ester.
Methyl carbamate or other carbamates can be added in stoichiometric
proportions to limonene or dipentene, but preferably the carbamate
is in substantial excess and functions as solvent and catalyst
moderator as well as reactant. It is preferred in accordance with
this invention to use from 50% to 800% stoichiometric excess of the
carbamate, preferably about 300% excess of the carbamate.
The Lewis acid catalysts useful in this invention include soluble
acid catalysts such as boron trifluroide etherate BF.sub.3.
Et.sub.2 O and solid acid catalysts, such as sulfonic acid, e.g.,
Amberlyst-15.RTM. available from the Rohm & Haas Company and
polysulfonic acid resin, e.g., Nafion-H.RTM. available from the Du
Pont Company. Other suitable acid catalysts include sulfuric acid,
toluene sulfonic acid, dodecylbenzene sulfonic acid, hydrocarbon
sulfate esters, hydrochloric acid, and the like.
The amount of catalyst required to promote the addition of
dipentene and carbamic acid ester is not critical and can be varied
widely. Where substantial excess of carbamic acid ester is utilized
the amount of catalyst, based on the diol is typically 0.01 to 10
mole % and preferably about 2 to 5 mole %.
The reaction can take place in the absence of solvent or in the
presence of solvents, such as methylene chloride, toluene, xylene,
chlorobenzene and so forth.
Preferably the carbamate is heated to maintain it molten, from
40.degree. C. to 150.degree. C. being suitable. The catalyst is
mixed into the molten carbamate, and the unsaturated hydrocarbon is
then slowly added. When the reaction is complete the mixture is
treated to remove or neutralize the catalyst. Unreacted carbamate
ester is then separated by distillation in partial vacuum or by
adding a large excess of water and filtering to separate insoluble
urethane products from water-soluble carbamate ester.
If excess of carbamate is employed this can also be distilled off
at partial vacuum and recovered. The recovered carbamate can be
recycled along with catalyst. The reaction mixture of urethanes,
unreacted carbamate ester, catalyst, and byproducts can also be
separated by adding a large excess of an aqueous medium, for
example, sodium carbonate solution to separate the urethane
products as insolubles and also to neutralize the catalyst.
Urethanes formed by the addition reaction of methyl carbamate and
limonene and useful in forming cyclohexyl isocyanates by thermal
cracking in accordance with this invention are generally designated
by the formulae: ##STR8##
Dipentene urethane esters form the corresponding isocyanate by
thermal cracking while splitting off the alkanol. In many cases the
alcohol can usefully be recycled by reaction with urea or isocyanic
acid (HNCO) to form the starting carbamate ester.
In cracking the urethane esters to form the corresponding
isocyanates the catalyst must be removed or neutralized for
example, with calcium oxide, sodium carbonate, sodium hydroxide and
the like, which is followed by cracking of the urethane ester
either solvent free or in high boiling solvents, such as
hexadecane, diphenyl ether, diisopropyl naphthalene and the like.
Cracking takes place at temperatures on the order of 150.degree. to
350.degree. C. during which the alkanol is split off to yield the
corresponding isocyanate.
The mono- and diurethanes obtained by the acid-catalyzed addition
reaction of dipentene and methyl urethane can be pyrolyzed or
cracked by a batch type method or on a continuous basis under
reduced, normal or increased pressure. The cleaving and sparating
of the products by distillation of the alcohol, possibly the
diisocyanate and any partially reacted monoisocyanate and any
unreacted diurethane, and/or optional solvent can take place
simultaneously or in a sequence. With simultaneous cleaving and
separation in the liquid phase, a temperature-pressure ratio is
advantageously chosen which corresponds to the boiling point of the
low boiling component of the bottom fraction.
Cracking of dipentene diurethane (DPDU) may be carried out in a
batch process without a catalyst at temperatures of 225.degree. to
350.degree. C. without a solvent. Optionally, a catalyst selected
from a group of metal oxides may be used, preferably with an inert
diluent such as high boiling hydrocarbons or silicones. The
reaction is preferably carried out at a temperature of from
225.degree. to 350.degree. C., most preferably at
235.degree.-260.degree. C., at a pressure of from 20 to 50 mm Hg,
most preferably at 35-45 mm Hg, in the presence of from 0.1 to 6
wt. percent, most preferably 0.5 to 3 wt. percent of a selective
metal oxide catalyst. The reaction time will vary, but usually from
about 2 to about 6 hours is sufficient. The progress of the
reaction can be followed as a fraction of time, e.g., by means of a
gas chromatograph.
It is another object of the invention to provide a process for
continuous cracking of dipentene diurethane (DPDU) and/or dipentene
monourethane (DPMU) to the desired isocyanates. The urethanes to be
cracked are continuously fed through a column packed with inert
supports such as glass helices, optionally impregnated or
physically mixed with metal oxides catalysts such as CaO, BaO and
the like. This results in increased throughput with minimal
by-products formation.
The product can be recovered in ways known to those skilled in this
art. Distillation is preferred, because it boils at
126.degree.-128.degree. C. under a 2 mm Hg vacuum and at
158.degree.-159.degree. C. under a 15 mm Hg vacuum.
To convert the isocyanates to curable reactants, it is convenient
to transform them to vinyl addition polymers or copolymers, e.g.,
by polymerizing them, alone, or in combination with a reactive
co-monomer, such as styrene or ethylene, using free radical or
other suitable polymerization conditions well known to those
skilled in the art. The resulting polyfunctional isocyanates can
then be mixed with a polyhydric compound, with or without solvents,
and optionally catalyzed with a tin or other conventional catalyst.
The polyhydric compound can comprise a polyol, e.g., trimethylol
propane or glycerol, a polyether polyol, e.g., polypropylene
glycol, a polyester polyol, e.g., poly(ethylene glycol adipate) a
polyamine, e.g., diethylene triamine, a polyamide, or it can
comprise water. Conventional functionalities will be selected, e.g,
0.5 to 5 mole of --NCO per mole of --OH, and curing will be
effected at 80.degree. to 150.degree. C. during 1 minute to 60
minutes, in the optional presence of 1% by weight of a catalyst,
e.g., dibutyl tin dilaurate.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following examples illustrate the processes and compounds of
the present invention and provide data to show their advantages
over the prior art. They are not to be construed to limit the
claims in any manner whatsoever.
In the Examples and Tables that follow, the following abbreviations
are used:
DP 1-methyl-4-(1-methylethenyl)cyclohexene; limonene; dipentene
MU carbamic acid methyl ester; methyl urethane; methyl
carbamate
DPMU dipentene monourethane
DPDU dipentene diurethane
DPDI dipentene diisocyanate
EXAMPLES 1-5
The following general method can be used to produce dipentene
diurethanes (DPDU) and dipentene monourethanes (DPMU) from
dipentene (DP) and methyl urethane (MU).
Addition reactions were carried out in flasks varying the quantity
of MU and the BF.sub.3. Et.sub.2 O catalyst. Reactions were carried
out without solvent at 60.degree. C. for 18 hours.
Compositions of the reaction mixtures and results are shown in
Table 1.
TABLE I ______________________________________ Addition of Methyl
Urethane (MU) to Di- pentene (DU) Using BF.sub.3.Et.sub.2 O
Catalyst* Example 1 2 3 4 5 ______________________________________
Composition (moles) Dipentene (DP) moles 5.0 5.0 5.0 5.0 5.0
Methylurethane (MU) moles 62 31 31 20 20 Boron trifluoride etherate
1.66 1.66 0.83 0.83 0.55 (BF.sub.3.Et.sub.2 O) mole
MU/BF.sub.3.Et.sub.2 O 37 18.7 37 24 36 eg MU/Olefin (C.dbd.C) 6.2
3.1 3.1 2.0 2.0 BF.sub.3.Et.sub.2 O/DP 0.33 0.33 0.17 0.17 0.11
Product Analysis (parts by percentage).sup.a Dienes 7 12 21 30 32
Dipentene Monourethane 44 37 34 35 32 (DPMU) Dipentene Diurethane
(DPDU) 44 47 43 33 33 ______________________________________ *All
addition reactions were carried out at 60.degree. C. for 18
hours.
The data in Examples 1 and 5 show that a one-third reduction in
catalyst loading (BF.sub.3. Et.sub.2 O) increases productivity (DP)
by two-fold with only a 10% reduction in DPDU yield. Thus, addition
reactions can be run using three times the amount of DP to produce
approximately 2.3 times the quantity of DPDU.
EXAMPLE 6
An addition reaction was carried out by following the method of
Examples 1-5 with the difference that a solid catalyst, sulfonic
acid was substituted for BF.sub.3.Et.sub.2 O.
The reaction was carried out in solvent-free methyl urethane (MU)
using a 12/1 MU/DP ratio at 62.degree. C. for 18 hours. The
sulfonic acid catalyst was Amberlyst-15.RTM. available from the
Rohm & Haas Company. The sulfonic acid catalyst level was about
33 mole percent (%) on the DP charged or approximately 0.5 g
Amberlyst.RTM./g DP (approximately 0.07 g/g total reaction
mixture). This level of catalyst is comparable to the levels of
BF.sub.3.Et.sub.2 O used in Examples 1 and 2. The reaction was
worked up by catalyst filtration, removal of excess MU by aqueous
extraction and distillation. Distillation provided the following
products analysis: 25% unreacted diene, 55% DPMU and 10%
bisurethane (DPDU).
EXAMPLE 7
An addition reaction was carried out following the method of
Example 6 except that a polysulfonic acid resin was used in place
of the sulfonic acid solid catalyst.
The polysulfonic acid resin employed in this procedure was
Nafion-H.RTM. polysulfonic acid resin available from the Du Pont
Company.
This reaction mixture gave a slightly higher conversion of DP
although yields of the diurethane were somewhat lower than with the
sulfonic acid catalyzed reactions.
EXAMPLE 8
DPDU was heated in a batch operation with three times its weight of
silicone oil. The silicone oil employed in this procedure was SF
96(-50).RTM. available from General Electric Company. This resulted
in near quantitative conversion to a 90/10 mixture of DPDI and
mono-olefin-isocyanate after one hour at a temperature greater than
235.degree. C. While product could be recovered from this
DPDI/silicone oil mixture by vacuum stripping, a more desirable
alternative was continuous product removal as cracking occurred.
This was done by gradually adding a toluene solution of DPDU to a
pool of hot silicone oil and continuously sweeping volatile
products from the reaction flask on a stream of nitrogen. The oil
was maintained at a temperature of 240.degree.-245.degree. C.
EXAMPLE 9
The procedure of Example 8 was followed with the difference that
the temperature for cracking was 260.degree.-265.degree. C. instead
of 235.degree. C. or greater.
Results indicate that cracking was relatively complete, with 53%
DPDI and 20% monoisocyanate-monoolefin along with 10% DPDU and 10%
monoisocyanate-monourethane being recovered.
EXAMPLE 10
The procedure of Example 8 was followed except that the DPDU was
heated in hexadecane solution instead of silicone oil and at a
temperature of 280.degree.-290.degree. C. instead of 235.degree. C.
or greater.
Results obtained by this procedure showed that DPDU could be
cracked to DPDI to a yield of approximately 90%.
EXAMPLE 11
A vertical tube reactor, electrically heated is packed with glass
helices. This is heated to 310.degree.-325.degree. C. and, at
atmospheric pressure, a solution of 20 percent by weight of
dipentene diurethane is fed into the top of the reactor at a rate
of 2 g. of urethane per hour. Nitrogen is used to sweep the flow
downward, and a cooled receiver at the bottom is employed to
collect the products. The corresponding dipentene diisocyanate is
obtained in good yield with greater than 90 percent material
recovery. When the corresponding monourethanes are substituted,
high yields of the corresponding monoisocyanates are also obtained
in this continuous process.
EXAMPLE 12
The procedure of Example 11 was repeated with glass helices coated
with powdered calcium oxide. Again, high yields of the isocyanates
were obtained with over 90 percent material recovery at a feed rate
of 2 g. per hour of urethane.
EXAMPLE 13
The procedure was repeated with a mixture of granular calcium oxide
and glass helices in the heated reaction zone. Substantially the
same results were obtained.
EXAMPLE 14
A curable composition is prepared by reacting a hydrocarbon solvent
solution comprising equal molar amounts of the diisocyanate of
Example 9, DPDI, and ethylene, catalyzed with 0.5 percent by weight
of azobisisobutyronitrile, at 80.degree. C. for 16 hours.
Evaporation of the solvent will leave a copolymer of DPDI and
ethylene as a residue. This will cure on exposure to moisture to a
composition utility as an adhesive or as a protective film.
If the composition is mixed in a solvent with trimethylol propane,
or with diethylene triamine, at an --NCO/--OH ratio of 1.1:1, using
1% by weight of tin (TRS), upon evaporation of the solvent and
heating at 100.degree. C. for 20 minutes, a solvent resistant hard
film should be obtained.
The above-mentioned patents and publications are incorporated by
reference.
Many variations will suggest themselves to those skilled in the art
in light of the above, detailed description. For example, instead
of using the methyl ester of carbamic acid in the addition
reaction, the ethyl, propyl, butyl, triacontyl or any of the higher
alkyl esters of carbamic acid can be used. Instead of boron
trifloride etherate or the sulfonic acid ion exchange resin, other
catalysts such as concentrated sulfuric acid, can be employed.
All such obvious variations are within the full intended scope of
the appended claims.
* * * * *